Heat pipe

ABSTRACT

A heat pipe has a heat receiving portion that is to be thermally connected to a heat generating member so as to absorb heat from the heat generating member. The heat pipe includes a sealed flat container; a wick structure housed inside the flat container; and a working fluid sealed inside the flat container. In at least one cross section of the flat container, the wick structure includes a first wick member and a second wick member disposed vertically, the wick structure also has a first wick part and a second wick part respectively disposed in the lengthwise direction of the flat container, the second wick part having a maximum width that is wider than a maximum width of the first wick part. The second wick part is disposed in the heat receiving portion of the heat pipe.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a thin heat pipe having a favorablemaximum heat transport amount, low thermal resistance, and excellentheat transport characteristics.

Background Art

Electronic components, such as semiconductor elements, that are mountedon electronic devices have increased in the amount of heat generated dueto higher mounting density associated with higher performance, and thuscooling of the components has become more important. One method forcooling electronic components is to use a heat pipe.

Due to narrowing of the installation area for the heat pipe caused bythe higher mounting density of the electronic components, and due to thesmaller size of the electronic components, there is demand for flat heatpipes, such as a thin heat pipe that has a thickness of 1.5 mm or below.There has been a proposal for a thin heat pipe that uses a wick having amain body and a first protruding part extending from the main body. Thefirst protruding part divides the inside of a heat-receiving part into afirst section communicating with a steam flow path and a second sectioncommunicating with a liquid return flow path, and the heat-receivingpart is thermally connected to a heat generating component at a locationstraddling the first section and the first protruding part (PatentDocument 1).

In Patent Document 1, the boundary between the first protruding part andsecond section can be disposed in a position far away from the heatgenerating component, which thus prevents an increase in pressure lossin this direction and the flowing of air bubbles in evaporated workingfluid in this direction. By extension, this prevents a reverse flowbeing generated in the working fluid and inhibits a reduction in heattransport efficiency, even if a plurality of heat generating componentsare provided.

However, the thin heat pipe in Patent Document 1 is problematic in thatit is not possible to attain both an improvement in the maximum heattransport amount and a reduction in thermal resistance; i.e., if themaximum heat transport amount is increased, then thermal resistance alsoincreases, and if thermal resistance is decreased, then the maximum heattransport amount also decreases. Thus, the thin heat pipe of PatentDocument 1 still had these aforementioned issues, which have aparticularly marked occurrence when the heat pipe is thin.

RELATED ART DOCUMENT

Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open Publication    No. 2009-204254

SUMMARY OF THE INVENTION

In view of the issues described above, the present invention aims atproviding a heat pipe that has excellent heat transport characteristicswith a favorable maximum heat transport amount and low thermalresistance even when the heat pipe is thin.

Additional or separate features and advantages of the invention will beset forth in the descriptions that follow and in part will be apparentfrom the description, or may be learned by practice of the invention.The objectives and other advantages of the invention will be realizedand attained by the structure particularly pointed out in the writtendescription and claims thereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, in oneaspect, the present disclosure provides a heat pipe having a heatreceiving portion that is configured to be thermally connected to a heatgenerating member so as to absorb heat from the heat generating member,the heat pipe including: a flat container having a tube shape of whichboth ends are sealed, the flat container having a pair of flat innersurfaces that oppose each other in a vertical direction in crosssections perpendicular to a lengthwise direction of the flat container;a wick structure housed inside the flat container; and a working fluidsealed inside the flat container, wherein in at least one cross sectionof the flat container: the wick structure includes a first wick memberand a second wick member disposed in the vertical direction, the firstwick member contacts the second wick member and one inner surface of thepair of flat inner surfaces of the flat container, and both side facesof the first wick member do not contact any of the inner surfaces of theflat container, and the second wick member contacts the other innersurface of the pair of flat inner surfaces of the flat container, andboth side faces of the second wick member do not contact any of theinner surfaces of the flat container, wherein the wick structure has afirst wick part and a second wick part, respectively disposed in thelengthwise direction of the flat container, the second wick part beingdirectly or indirectly connected to the first wick part and having amaximum width that is wider than a maximum width of the first wick part,and wherein the second wick part is disposed in the heat receivingportion of the heat pipe.

In an aspect of the heat pipe of the present invention, the maximumwidth of the first wick part is 40% to 60% of a maximum width of aninner space of the flat container, and the maximum width of the secondwick part is 60% to 80% of the maximum width of the inner space of theflat container.

In the aforementioned aspect, a maximum width of the first wick part is40% to 60% relative to the width in the direction (cross section of theflat container) orthogonal to the lengthwise direction inside the flatcontainer; thus, on the pair of flat inner surfaces of the flatcontainer corresponding to the position of the first wick part, there isa location that does not contact either the first wick member or thesecond wick member, and this location is exposed to the inner space ofthe flat container. Moreover, a maximum width of the second wick part is60% to 80% relative to the width in the direction (cross section of theflat container) orthogonal to the lengthwise direction inside the flatcontainer; thus, on the pair of flat inner surfaces of the flatcontainer corresponding to the position of the second wick part, thereis a location that does not contact either the first wick member or thesecond wick member, and this location is exposed to the inner space ofthe flat container. Furthermore, the exposed region of the flat innersurfaces of the flat container corresponding to the position of thefirst wick part is wider than the exposed region of the flat innersurfaces of the flat container corresponding to the position of thesecond wick part.

In an aspect of the heat pipe of the present invention, a length of thesecond wick part in the lengthwise direction of the flat container is 2%to 50% of a sum of a length of the first wick part in the lengthwisedirection of the flat container and a length of the second wick part inthe lengthwise direction of the flat container.

In an aspect of the heat pipe of the present invention, in the at leastone cross section: a cross section of the first wick member has aconvex-shaped bottom and a flat top, and a cross section of the secondwick member has a flat bottom and a convex-shaped top, and theconvex-shaped bottom of the first wick member contacts the convex-shapedtop of the second wick member, and the flat top of the first wick membercontacts the one inner surface, and the flat bottom of the second wickmember contacts the other inner surface.

In the aforementioned aspect, the convex-shaped bottom of the first wickmember and the convex-shaped top of the second wick member contact eachother; thus, locations of the convex-shaped bottom and convex-shaped topother than those contacting the other convex-shaped part are exposed tothe inner space of the flat container.

In an aspect of the heat pipe of the present invention, the second wickpart of the wick structure is in the at least one cross section, and inthe at least one cross section, a maximum width of the flat bottom orthe convex top of the second wick member is 60% to 80% of a maximumwidth of an inner space of the flat container.

In an aspect of the heat pipe of the present invention, the first wickpart is disposed on one end in the lengthwise direction of the flatcontainer, and the second wick part is disposed on the other end in thelengthwise direction of the flat container.

In an aspect of the heat pipe of the present invention, there are twofirst wick parts, and one of the first wick parts is disposed on one endin the lengthwise direction of the flat container, and the other of thefirst wick parts is disposed on the other end in the lengthwisedirection of the flat container, the second wick part being disposed ina center in the lengthwise direction of the flat container.

In an aspect of the present invention, the heat pipe further includes athird wick part disposed between the first wick part and the second wickpart in the lengthwise direction of the flat container, the third wickpart having a maximum width that is wider than the maximum width of thefirst wick part and narrower than the maximum width of the second wickpart.

In an aspect of the heat pipe of the present invention, in the at leastone cross section, the side faces of the first wick member that do notcontact any of the inner surfaces of the flat container have a convexshape, and the side faces of the second wick member that do not contactany of the inner surfaces of the flat container have a convex shape.

In an aspect of the heat pipe of the present invention, the first wickpart and the second wick part are sintered metal compacts.

In an aspect of the heat pipe of the present invention, the sinteredmetal compact of the second wick part is formed of sintered powdershaving a finer particle size than sintered powders of the sintered metalcompact of the first wick part.

In an aspect of the heat pipe of the present invention, the pair of flatinner surfaces opposing each other are vertically separated by adistance of 1.5 mm or less.

In the aforementioned aspect, the flat container has the pair of flatinner surfaces that oppose each other (i.e., one inner surface andanother inner surface that opposes the one inner surface), and thedistance between the opposing flat inner faces is 1.5 mm or less.

In an aspect of the heat pipe of the present invention, in every crosssection of the wick structure, the wick structure includes the firstwick member and the second wick member disposed in the verticaldirection.

In an aspect of the heat pipe of the present invention, in every crosssection of the wick structure: the wick structure includes the firstwick member and the second wick member disposed in the verticaldirection; the first wick member contacts the second wick member and theone inner surface of the pair of flat inner surfaces of the flatcontainer, and the side faces of the first wick member do not contactany of the inner surfaces of the flat container; and the second wickmember contacts the other inner surface of the pair of flat innersurfaces of the flat container, and the side faces of the second wickmember do not contact any of the inner surfaces of the flat container.

In an aspect of the heat pipe of the present invention further includesa thermally conductive member attached to the heat receiving portion ofthe heat pipe so as to be thermally connected to the heat generatingmember.

In an aspect of the heat pipe of the present invention, in a crosssection of the heat receiving portion of the heat pipe that is differentfrom the at least one cross section: the wick structure includes thefirst wick member and the second wick member disposed in the verticaldirection; the first wick member contacts the one inner surface of thepair of flat inner surfaces of the flat container, and the side faces ofthe first wick member do not contact any of the inner surfaces of theflat container; the second wick member contacts the other inner surfaceof the pair of flat inner surfaces of the flat container, and the sidefaces of the second wick member do not contact any of the inner surfacesof the flat container; and the first wick member does not contact thesecond wick member.

According to an aspect of the present invention, when a heat pipe has afirst wick part and a second wick part that has a wider maximum widththan the first wick part, and a location of the heat pipe contacting aheat generating member is regarded as a heat receiving portion, thepositioning of the second wick part at the heat receiving portion makesit possible to obtain, even if the heat pipe is thin, excellent heattransport characteristics with an excellent maximum heat transportamount and reduced thermal resistance.

According to an aspect of the present invention, the heat pipe has thefirst wick part and the second wick part that is formed as the heatreceiving portion, wherein the first wick part has a maximum width of40% to 60% relative to the maximum width of a cross section of a flatcontainer, and the second wick part has a maximum width that is widerthan the first wick part and 60% to 80% relative to the maximum width ofthe cross section of the flat container; thus, even if the heat pipe isthin, it is possible to obtain even better heat transportcharacteristics with reduced thermal resistance and an excellent maximumheat transport amount.

According to an aspect of the present invention, the length of thesecond wick part in the lengthwise direction of the flat container is 2%to 50% of the sum of the length of the first wick part and the length ofthe second wick part in the lengthwise direction of the flat container,thus making it possible to further reduce thermal resistance whileimproving the maximum heat transport amount.

According to an aspect of the present invention, the cross section ofthe first wick member has a convex-shaped bottom side part and a flattop side part, and the cross section of the second wick member has aflat bottom side part and a convex-shaped top side part, and the maximumwidth of the bottom side part or top side part of the second wick partis 60% to 80% relative to the maximum width of the cross section of theflat container, thus making it possible to further reduce thermalresistance while improving the maximum heat transport amount.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a planar cross-sectional view of a heat pipe according toEmbodiment 1 of the present invention, FIG. 1B is a cross-sectional viewalong a-a in FIG. 1A, and FIG. 1C is a cross-sectional view along b-b inFIG. 1A.

FIG. 2A is a planar cross-sectional view of a heat pipe according toEmbodiment 2 of the present invention, FIG. 2B is a cross-sectional viewalong a-a in FIG. 2A, and FIG. 2C is a cross-sectional view along b-b inFIG. 2A.

FIG. 3 is a planar cross-sectional view of a heat pipe according toEmbodiment 3 of the present invention.

FIG. 4 is a planar cross-sectional view of a heat pipe according toEmbodiment 4 of the present invention.

FIG. 5A is a side view of a heat pipe according to another embodiment ofthe present invention, FIG. 5B is a cross-sectional view along a-a inFIG. 5A, and FIG. 5C is a cross-sectional view along b-b in FIG. 5A.

FIG. 6A is a side view of a heat pipe according to another embodiment ofthe present invention, FIG. 6B is a cross-sectional view along a-a inFIG. 6A, and FIG. 6C is a cross-sectional view along b-b in FIG. 6A.

FIG. 7 is a diagram for explaining a heat pipe according to anotherembodiment of the present invention.

FIG. 8A is a side view of a heat pipe according to another embodiment ofthe present invention, FIG. 8B is a cross-sectional view along a-a inFIG. 8A, and FIG. 8C is a cross-sectional view along b-b in FIG. 8A.

FIG. 9A is a side view of a heat pipe according to another embodiment ofthe present invention, FIG. 9B is a cross-sectional view along a-a inFIG. 9A, and FIG. 9C is a cross-sectional view along b-b in FIG. 9A.

FIG. 10A is a side view of a heat pipe according to another embodimentof the present invention, FIG. 10B is a cross-sectional view along a-ain FIG. 10A, and FIG. 10C is a cross-sectional view along b-b in FIG.10A.

DETAILED DESCRIPTION OF EMBODIMENTS

A heat pipe according to Embodiment 1 of the present invention will bedescribed below with reference to the drawings.

As shown in FIGS. 1A to 1C, a heat pipe 1 according to Embodiment 1includes a tube shaped flat container 10 having one flat inner surface11 and another flat inner surface 12 opposing the one flat inner surface11, a first wick member 21 disposed on the one flat inner surface 11, asecond wick member 22 disposed on the other flat inner surface 12, and aworking fluid (not shown) sealed inside the flat container 10.

As shown in FIGS. 1B and 1C, the flat container 10 is a sealed straighttube member that has the one flat inner surface 11 and the other flatinner surface 12 opposing the one flat inner surface 11, and curvedsections 13 and 13′ formed between the one flat inner surface 11 and theother flat inner surface 12. The cross-sectional shape of the flatcontainer in a direction orthogonal to the lengthwise direction (i.e.,the cross-sectional shape perpendicular to the lengthwise direction) isa flat shape. In other words, the flat container 10 has a pair of flatinner surfaces that oppose each other in the vertical direction in across section perpendicular to the lengthwise direction. The entirety ofthe flat container 10 in the lengthwise direction thereof is a flatshape. Furthermore, the cross-sectional area of the inner space of theflat container 10 in the direction orthogonal to the lengthwisedirection is the same at all locations, and the one flat inner surface11 is formed in a direction parallel to the other flat inner surface 12.Moreover, the distance between the one flat inner surface 11 and theother flat inner surface 12 is not particularly limited, but is 1.5 mmor less in the flat container 10, or in particular, a thin shape of 1.0mm or less. The heat transport direction of the heat pipe 1 is thelengthwise direction of the flat container 10.

The first wick member 21 has a first curved section 23, which is aconvex-shaped bottom side part of a convex shape protruding from the oneflat inner surface 11, and a flat top side part 25, which contacts partof the one flat inner surface 11. In the heat pipe 1, the flat top sidepart 25 is adhered to the one flat inner surface 11. The first wickmember 21 is provided in the center of the flat container 10 in thedirection orthogonal to the lengthwise direction of the flat container10 (in a cross section of the flat container 10). In the heat pipe 1,the cross-sectional shape of the first wick member 21 in the directionorthogonal to the lengthwise direction of the flat container 10 is asemi-elliptical shape.

The second wick member 22 has a second curved section 24, which is aconvex-shaped top side part of a convex shape opposing the first curvedsection 23 that is the convex-shaped bottom side part of the convexshape protruding from the other flat inner surface 12, and a flat bottomside part 26, which contacts part of the other flat inner surface 12. Inthe heat pipe 1, the flat bottom side part 26 is adhered to the otherflat inner surface 12. The second wick member 22 is provided in thecenter of the flat container 10 in the direction orthogonal to thelengthwise direction of the flat container 10. In the heat pipe 1, thecross-sectional shape of the second wick member 22 in the directionorthogonal to the lengthwise direction of the flat container 10 is asemi-elliptical shape.

In the heat pipe 1, the region of the one flat inner surface 11 of theflat container 10 not contacting the flat top side part 25 of the firstwick member 21, and the region of the other flat inner surface 12 of theflat container 10 not contacting the flat bottom side part 26 of thesecond wick member 22, and the curved sections 13 and 13′ of the flatcontainer 10, are all exposed to the inner space of the flat container10.

The first curved section 23 of the first wick member 21 contacts thesecond curved section 24 of the second wick member 22. In the heat pipe1, the bottom of the first curved section 23 and the top of the secondcurved section 24 contact each other. The bottom of the first curvedsection 23 and the top of the second curved section 24 are both in astate of pressure contact with each other. Accordingly, the bottom ofthe first curved section 23 and the top of the second curved section 24are compressed and deformed. This can further improve the capillarypressure of the first wick member 21 and the second wick member 22 andcause the working fluid in the liquid phase to circulate more smoothly.

As shown in FIG. 1B, on one end of the flat container 10, a first wickpart 31 made of the first wick member 21 and the second wick member 22is formed. The maximum widths of the flat top side part 25 and flatbottom side part 26 in the first wick part 31 in the directionorthogonal to the lengthwise direction of the flat container 10 are 40%to 60% of the maximum width of the inner space of the flat container 10in the direction orthogonal to the lengthwise direction of the flatcontainer. The first wick part 31 of the heat pipe 1 has across-sectional shape in the direction orthogonal to the lengthwisedirection of the flat container 10 that has approximately the same shapeand dimensions at all locations in the lengthwise direction of the flatcontainer 10. Accordingly, the widths of the flat top side part 25 andflat bottom side part 26 in the direction orthogonal to the lengthwisedirection of the flat container are approximately uniform in the firstwick part 31 along the lengthwise direction of the flat container 10.

In contrast, as shown in FIG. 1C, on the other end of the flat container10, a second wick part 32 made of the first wick member 21 and thesecond wick member 22 is formed. Accordingly, the wick structure, whichis made of the first wick member 21 and the second wick member 22, hasthe first wick part 31 and the second wick part 32. The maximum widthsof the flat top side part 25 and flat bottom side part 26 in the secondwick part 32 in the direction orthogonal to the lengthwise direction ofthe flat container 10 are 60% to 80% of the maximum width of the innerspace of the flat container 10 in the direction orthogonal to thelengthwise direction of the flat container. Moreover, theabove-mentioned widths (in the direction orthogonal to the lengthwisedirection of the flat container) of the flat top side part 25 and flatbottom side part 26 of the second wick part 32 are always wider than thewidths (in the direction orthogonal to the lengthwise direction of theflat container) of the flat top side part 25 and flat bottom side part26 of the first wick part 31. The second wick part 32 of the heat pipe 1has a cross-sectional shape in the direction orthogonal to thelengthwise direction of the flat container 10 that has approximately thesame shape and dimensions at all locations in the lengthwise directionof the flat container 10. Accordingly, the widths of the flat top sidepart 25 and flat bottom side part 26 are also approximately uniform atthe second wick part 32 in the lengthwise direction of the flatcontainer 10.

As shown in FIG. 1A, in the heat pipe 1, the first wick part 31 made ofthe first wick member 21 and second wick member 22 is formed at alocation between one end and another end of the flat container 10, ornamely, is formed in the center of the flat container 10 in a similarmanner to the one end of the flat container 10.

In the heat pipe 1, the second wick part 32 functions as a heatreceiving portion of the heat pipe 1, and the first wick part 31functions as a heat dissipating part of the heat pipe 1. In order tofunction as a heat receiving portion, a heat generating member (notshown) is thermally connected to a prescribed location of the flatcontainer 10. When thermally connecting the heat generating member tothe prescribed location of the flat container 10, a thermally conductivemember such as a metal heat receiving plate, thermally conductiverubber, or thermal rubber may be provided between the prescribedlocation and the heat generating member as necessary. Furthermore, inorder to function as a heat dissipating part, a heat exchange member(not shown) such as heat radiating fins or heat sink, for example, isthermally connected to a prescribed location of the flat container 10.

In the heat pipe 1, the width of the second wick part 32 in thedirection orthogonal to the lengthwise direction of the flat containeris greater than the width of the first wick part 31 in the directionorthogonal to the lengthwise direction of the flat container.Furthermore, the width of the second wick part 32 in the directionorthogonal to the lengthwise direction of the flat container is 60% to80% relative to the width of the flat container 10, and the width of thefirst wick part 31 in the direction orthogonal to the lengthwisedirection of the flat container is 40% to 60% relative to the width ofthe flat container 10. This makes it possible to achieve excellent heattransport characteristics with reduced thermal resistance and anexcellent maximum heat transport amount, even if the container is thin.

As shown in FIG. 1A, in the heat pipe 1, the first wick member 21 andsecond wick member 22 (not shown in FIG. 1A) both extend in a straightline in a direction from one end to the other end of the flat container10, or namely, in the direction parallel to the lengthwise direction ofthe flat container 10. Both the first wick member 21 and second wickmember 22 (not shown in FIG. 1A) are configured such that the width ofthe second wick part 32 in the direction orthogonal to the lengthwisedirection of the flat container 10 is wider than the width of the firstwick part 31 and a step 33 is formed at the boundary between the firstwick part 31 and the second wick part 32. The boundary between the firstwick part 31 and the second wick part 32 need not be a step, and thewidth may gradually change instead.

The length of the second wick part 32 in the lengthwise direction of theflat container 10 has no particular limitations, but is preferably 2% to50% of the sum of the length of the first wick part 31 and the length ofthe second wick part 32 in the lengthwise direction of the flatcontainer 10, so as to have a favorable balance between the increase inmaximum heat transport amount and decrease in thermal resistance.Furthermore, the lengths in the lengthwise direction of the flatcontainer 10 of the flat top side part 25 and flat bottom side part 26of the second wick part 32 have no particular limitations, but arepreferably 1.0 to 5.0 times the length of the heat generating memberthermally connected to the heat receiving portion, so as to have afavorable balance between the increase in maximum heat transport amountand decrease in thermal resistance. Moreover, the widths of the flat topside part 25 and flat bottom side part 26 of the second wick part 32 inthe direction orthogonal to the lengthwise direction of the flatcontainer 10 have no particular limitations, but are preferably 0.50 to1.5 times the width of the heat generating member thermally connected tothe heat receiving portion, so as to have a favorable balance betweenthe increase in maximum heat transport amount and decrease in thermalresistance.

As shown in FIGS. 1A to 1C, the locations in the inner space of the flatcontainer 10 where the first wick member 21 and second wick member 22are not disposed function as a steam flow path 34 for the working fluidin the gas phase. In other words, the steam flow path 34 is formed fromthe region of the one flat inner surface 11 not contacting the firstwick member 21, the surface of the first curved section 23, the regionof the other flat inner surface 12 not contacting the second wick member22, the surface of the second curved section 24, and the curved sections13 and 13′ of the flat container 10. Accordingly, the steam flow path 34extends in a straight line in the direction parallel to the lengthwisedirection of the flat container 10, and the steam flow path 34 on thefirst wick part 31 side is wider than the steam flow path 34 on thesecond wick part 32, with the step 33 as the boundary. The steam flowpath 34 is provided on both sides of the first wick member 21 and thesecond wick member 22.

The material of the flat container 10 has no particular limitations, andcan be copper, to have excellent thermal conductivity; aluminum, to belightweight; stainless steel, to improve strength; or the like. Thematerial of the first wick member 21 and second wick member 22 has noparticular limitations, and can be a metal powder such as copper powderor stainless steel powder, carbon powder, a mixed powder of copperpowder and carbon powder, nanoparticles of the aforementioned powders, asintered compact such as a composite alloy in which a metal mesh andmetal powder have been combined, or the like. The sintered compact canbe manufactured by sintering the aforementioned powders or compositemetal to bond the powder, and forming a porous structure havingcapillary pressure by sintering. It is preferable that the sinteredmetal compact of the second wick part 32 be formed of a sintered powderhaving a finer particle size than the sintered metal compact of thefirst wick part 31, in order to improve the capillary force of thesecond wick part 32 over the capillary force of the first wick part 31and to smoothly circulate the working fluid in the liquid phase to theheat receiving portion.

The working fluid sealed in the flat container 10 can be selected asappropriate based on compatibility with the material of the flatcontainer 10, and examples of the working fluid include water,alternative chlorofluorocarbon, perfluorocarbon, or cyclopentane.

Next, the heat transport mechanism of the heat pipe 1 according toEmbodiment 1 of the present invention will be explained. When the heatpipe 1 receives heat from the heat generating member thermally connectedat the heat receiving portion, the working fluid changes phases from aliquid phase to a gas phase at the heat receiving portion. The gas phaseworking fluid flows through the steam flow path 34 from the heatreceiving portion to the heat dissipating part in the lengthwisedirection of the flat container 10, thereby transporting the heat fromthe heat generating member to the heat dissipating part from the heatreceiving portion. The heat from the heat generating part that has beentransported from the heat receiving portion to the heat dissipating partchanges phases from a gas phase working fluid to a liquid phase workingfluid at the heat dissipating part provided with the heat exchangemember, thus being discharged as latent heat. The latent heat dischargedat the heat dissipating part is discharged from the heat dissipatingpart to the external environment of the heat pipe 1 via the heatexchange member provided to the heat dissipating part. The working fluidthat has changed phases to a liquid phase at the heat dissipating partis taken into the first wick member 21 and second wick member 22 and isreturned from the heat dissipating part to the heat receiving portion bythe capillary pressure of the first wick member 21 and the second wickmember 22.

Next, a heat pipe according to Embodiment 2 of the present inventionwill be described below with reference to the drawings. The samereference characters are used for the same components as the heat pipeof Embodiment 1.

In the heat pipe 1, the first wick part 31 was disposed at one end andthe center in the lengthwise direction of the flat container 10, and thesecond wick part 32 was disposed at the other end. Instead of thisconfiguration, in the heat pipe 2 of Embodiment 2, as shown in FIGS. 2Ato 2C, a second wick part 32 is disposed in the center in the lengthwisedirection of the flat container 10, and first wick parts 31 arerespectively disposed at both ends in the lengthwise direction of theflat container 10. In other words, there are two first wick parts 31.Accordingly, in the heat pipe 2, the center in the lengthwise directionof the flat container 10 functions as the heat receiving portion, andthe one end and other end in the lengthwise direction of the flatcontainer 10 function as heat dissipating parts. The first wick parts 31are provided on both ends of the second wick part 32; thus, there aretwo boundaries between the first wick parts 31 and second wick part 32,and thus there are two steps 33 formed.

The heat pipe 2 also makes it possible to achieve excellent heattransport characteristics with reduced thermal resistance and anexcellent maximum heat transport amount. Furthermore, in the heat pipe2, a plurality (two in the drawings) of heat dissipating parts can beprovided, which further improves the cooling efficiency of the heatgenerating member.

Next, a heat pipe according to Embodiment 3 of the present inventionwill be described below with reference to the drawings. The samereference characters are used for the same components as the heat pipesof Embodiments 1 and 2.

In the heat pipe 1 according to Embodiment 1, the first wick member 21and second wick member 22 were not provided at both end faces in thelengthwise direction of the flat container 10, but rather the entiretyof both end faces was exposed to the inner space of the flat container10; however, instead of this configuration, in the heat pipe 3 ofEmbodiment 3, as shown in FIG. 3, a first wick member 21 and a secondwick member 22 (not shown) extend up to both end faces 14 in thelengthwise direction of the flat container 10. Accordingly, both endfaces of the first wick member 21 and the second wick member 22 in thelengthwise direction of the flat container 10 contact both end faces 14in the lengthwise direction of the flat container 10.

The heat pipe 3 also makes it possible to achieve excellent heattransport characteristics with reduced thermal resistance and anexcellent maximum heat transport amount.

Next, a heat pipe according to Embodiment 4 of the present inventionwill be described below with reference to the drawings. The samereference characters are used for the same components as the heat pipesof Embodiments 1 to 3.

In the heat pipe 2 according to Embodiment 2, the first wick member 21and second wick member 22 were not provided at both end faces in thelengthwise direction of the flat container 10, but rather the entiretyof both end faces was exposed to the inner space of the flat container10; however, instead of this configuration, in the heat pipe 4 ofEmbodiment 4, as shown in FIG. 4, a first wick member 21 and a secondwick member 22 (not shown) extend up to both end faces 14 in thelengthwise direction of the flat container 10. Accordingly, both endfaces 14 of the first wick member 21 and the second wick member 22 inthe lengthwise direction of the flat container 10 contact both end facesin the lengthwise direction of the flat container 10.

The heat pipe 4 also makes it possible to achieve excellent heattransport characteristics with reduced thermal resistance and anexcellent maximum heat transport amount.

Next, an example of a method of manufacturing the heat pipe of thepresent invention will be described. The method of manufacturing has noparticular limitations; however, as an example, for the heat pipeaccording to Embodiment 1, a core rod having a cutout of a prescribedshape is inserted along the lengthwise direction of a round tube member,and a metal material in powdered form, which will become the first wickmember and second wick member, is filled into a cavity between the innerwall faces of the tube member and the outer faces of the cutout. Thecutout of the core rod has a small cutout corresponding to the positionof the first wick part and a large cutout corresponding to the positionof the second wick part. Next, a thermal treatment is applied to form aprecursor of the first wick member and a precursor of the second wickmember. Thereafter, the core rod is removed from the small cutout sideand the tube member is flattened to manufacture a heat pipe having thefirst wick member and the second wick member.

The heat pipe according to Embodiment 2 can be manufactured in a similarmanner to the heat pipe according to Embodiment 1, but instead of thecore rod used in the heat pipe of Embodiment 1, a first core rod havinga small cutout corresponding to the position of the first wick part anda large cutout corresponding to the position of the second wick part isinserted from one end of the round tube member up to the center in thelengthwise direction, and a second rod part having a small cutoutcorresponding to the position of the first wick part is inserted fromthe other end of the round tube member. After the filling of thepowdered metal material and heat treatment, the first core rod isremoved from the small cutout side at the one end side of the tubemember, and the second core rod is removed from the other end side, thusmaking it possible to manufacture the heat pipe of Embodiment 2.

Next, other embodiments of the present invention will be explained. Inthe heat pipes of the respective embodiments above, a second wick parthaving a wide width in the direction orthogonal to the lengthwisedirection of the flat container was disposed adjacent to a first wickpart for which the width is narrow, but instead of this configuration, athird wick part for which the width is wider than the first wick partand narrower than the second wick part may be provided between the firstwick part and the second wick part. The width of the third wick part maybe uniform, or may gradually expand from the first wick part to thesecond wick part.

In the heat pipe of Embodiment 1, the first wick part for which thewidth is narrow was formed in the center of the flat container in asimilar manner to the one end of the flat container, but instead of thisconfiguration, a second wick part for which the width is wide may beformed in a similar manner to the other end of the flat container. Inthe heat pipes of the respective embodiments above, the first wick partand the second wick part each had, in the lengthwise direction of theflat container, a width of the flat top side part and width of the flatbottom side part in the direction orthogonal to the lengthwise directionof the flat container that were approximately uniform, but instead ofthis configuration, the widths need not necessarily be approximatelyuniform, and may gradually widen, or may repeatedly widen and contract,or the like, for example, as long as the widths are within the numericalranges described above.

In the heat pipes of the respective embodiments above, the entirety ofthe container in the lengthwise direction was a flat shape, but insteadof this configuration, a part in the lengthwise direction may be a flatshape.

In the heat pipes of the respective embodiments above, thecross-sectional shape of the first wick member and second wick memberwas a semi-elliptical shape, but the shape has no particular limitationsand may be rectangular, for example. In the heat pipes of the respectiveembodiments above, the first wick member and the second wick member wereboth provided in the center position in the direction orthogonal to thelengthwise direction of the flat container, but the first wick memberand second wick member are not limited to these positions, and may beprovided outside the center (at the ends, for example), or the firstwick member and the second wick member may be provided at differingpositions from each other (for example, one of the first wick member andthe second wick member may be provided in the center, and the other atthe end). In the heat pipes of the respective embodiments above, thebottom of the convex-shaped bottom side part and the top of theconvex-shaped top side part pressure contacted each other, but insteadof this configuration, the parts may contact each other withoutpressure.

In the heat pipes of the respective embodiments above, the bottom of theconvex-shaped bottom side part and the top of the convex-shaped top sidepart pressure contacted each other, but instead of this configuration, aconfiguration is possible in which the bottom of the convex-shapedbottom side part and the top of the convex-shaped top side part of thefirst wick part contact each other, and the bottom of the convex-shapedbottom side part and the top of the convex-shaped top side part of thesecond wick part do not contact each other, or a configuration in whichthe bottom of the convex-shaped bottom side part and the top of theconvex-shaped top side part of the second wick part, which requires highcapillary pressure, contact each other, and the bottom of theconvex-shaped bottom side part and the top of the convex-shaped top sidepart of the first wick part do not contact each other.

In such a case, as shown in FIGS. 5A to 5C, for example, a configurationis possible in which the thickness of the flat container changes at thecenter in the lengthwise direction of the flat container 10: at thethicker end of the flat container 10 (as shown in FIG. 5B, the end towhich heat radiating fins 101 are thermally connected), the first curvedsection 23 of the first wick member 21 and the second curved section 24of the second wick member 22 of the first wick part 31 do not contacteach other, but rather, at the thinner end of the flat container 10 (asshown in FIG. 5C, the end to which a heat generating member 102 isthermally connected), the first curved section 23 of the first wickmember 21 and the second curved section 24 of the second wick member 22of the second wick part 32 contact each other.

Moreover, as shown in FIGS. 6A to 6C, a configuration is possible inwhich the thickness of the flat container changes at the center in thelengthwise direction of the flat container 10: at the thicker end of theflat container 10 (as shown in FIG. 6C, the end to which a heatgenerating member 102 is thermally connected), the first curved section23 of the first wick member 21 and the second curved section 24 of thesecond wick member 22 of the second wick part 32 do not contact eachother, but rather, at the thinner end of the flat container 10 (as shownin FIG. 6B, the end to which heat radiating fins 101 are thermallyconnected), the first curved section 23 of the first wick member 21 andthe second curved section 24 of the second wick member 22 of the firstwick part 31 contact each other.

In the heat pipes of the respective embodiments above, the flatcontainer is a tube member, and the cross-sectional shape thereof is asubstantially elliptical shape having a pair of flat inner surfaces thatvertically oppose each other, but there are no particular limitations onthe cross-sectional shape of the flat container, and the shape may be arectangle with corners, for example.

Furthermore, in the heat pipes of the respective embodiments above, thetube member flat container was a straight shape, but there are noparticular limitations on the shape in the lengthwise direction shape ofthe tube member; as shown in FIG. 7, for example, the tube container 10may be bent into an L-shape or the like, and a heat exchange member suchas the heat radiating fins 101 may be thermally connected to one end,and a heat generating member 102 may be thermally connected to the otherend.

In addition, as shown in FIG. 8A through FIG. 9C, the shape of the flatcontainer 10, which has a uniform thickness, may have a step-likelocation 15 in the center in the lengthwise direction of the flatcontainer 10. In such a case, at the end of the flat container 10 towhich the heat generating member 102 is thermally connected, the firstcurved section 23 of the first wick member 21 and the second curvedsection 24 of the second wick member 22 of the second wick part 32 maycontact each other, as shown in FIG. 8C, or may not contact each other,as shown in FIG. 9C. In a similar manner, at the end of the flatcontainer 10 to which the heat exchange member such as the heatradiating fins 101 is thermally connected, the first curved section 23of the first wick member 21 and the second curved section 24 of thesecond wick member 22 of the first wick part 31 may not contact eachother, as shown in FIG. 8B, or may contact each other, as shown in FIG.9B.

In the heat pipes of Embodiments 1 and 2, the cross section of the firstwick member and the cross section of the second wick member wereapproximately the same size (i.e., the width of the flat top side partand the width of the bottom side part were approximately the same), butinstead of this configuration, as shown in FIGS. 10A to 10C, the crosssection of the first wick member 21 may differ in size from the crosssection of the second wick member 22, or in other words, the width ofthe flat top side part 25 may differ from the width of the flat bottomside part 26. In such a case, if the maximum width of the second wickpart 32 is greater than the maximum width of the first wick part 31,then as shown in FIGS. 10B and 10C, the cross section of the first wickmember 21 may be larger than the cross section of the second wick member22, or namely, the width of the flat top side part 25 may be wider thanthe width of the flat bottom side part 26, or the cross section of thesecond wick member 22 may be larger than the cross section of the firstwick member 21, or namely, the width of the flat bottom side part 26 maybe wider than the width of the flat top side part 25. In such aconfiguration, it is possible to improve the contact area of the firstwick member 21 and second wick member 22 with the working fluid whilemore reliably securing the steam flow passage 34, thus further improvingheat transport characteristics of the heat pipe.

In the heat pipes of Embodiments 1 and 2, the distance between one flatinner surface of the flat container and the other flat inner surface, ornamely, the thickness of the flat container, was uniform, but instead ofthis configuration, the distance need not be uniform; for example, thethickness of the flat container corresponding to the position of thefirst wick part may differ from the thickness of the flat containercorresponding to the position of the second wick part (e.g., thethickness of the flat container corresponding to the position of thesecond wick part may be thinner than the thickness of the flat containercorresponding to the position of the first wick part).

In the heat pipe of Embodiment 2, one second wick part was disposed inthe center, but there are no particular limitations to the number ofsecond wick parts, and a plurality may be provided instead. In such acase, the first wick part and/or third wick part would be disposedbetween the adjacent second wick parts.

Working Example

Next, a working example of the present invention will be described, butthe present invention is not limited to this example.

As a working example, a configuration having the same structure as theheat pipe of Embodiment 1 was used. However, the maximum widths of thefirst wick part and second wick part were modified as indicated in Table1 below. For the container, a tube member with a length of 200 mm and φof 8 mm was flattened to 1 mm A 10 mm×20 mm and 15 W member was used asthe heat generating member. The heat generating member was made tocontact the other end of the container (heat pipe) where the second wickpart was formed, a thermocouple was installed at a location of 15 mmfrom the one end of the container (heat pipe) where the first wick partwas formed, and ΔT was measured.

ΔT was evaluated as “A” when 0° C. to 5° C., “B” when exceeding 5° C.but not more than 8° C., “C” when exceeding 8° C. but not more than 10°C., and “D” when exceeding 10° C.

The evaluation results are shown in Table 1 below.

TABLE 1 Maximum Width of First Wick Part 35% 40% 45% 50% 55% 60% 65%Maximum 55% C C C C C — — Width of 60% C B B B B C — Second 65% C B A AA B C Wick Part 70% C B A A A B C 75% C B A A A B C 80% C B B B B B C85% C C B D D C D

From Table 1, it can be seen that when a maximum width of the first wickpart relative to the maximum width in the direction (cross section)orthogonal to the lengthwise direction of the flat container is 40% to60% and a maximum width of the second wick part relative to the maximumwidth in the direction (cross section) orthogonal to the lengthwisedirection of the flat container is 60% to 80%, it gives at leastevaluation B, which offers excellent heat transport characteristics witha favorable maximum heat transport amount and reduced thermalresistance. In particular, when a maximum width of the first wick partrelative to the maximum width in the direction (cross section)orthogonal to the lengthwise direction of the flat container is 45% to55% and a maximum width of the second wick part relative to the maximumwidth in the direction (cross section) orthogonal to the lengthwisedirection of the flat container is 65% to 75%, it gives evaluation A,which offers extremely excellent heat transport characteristics.

INDUSTRIAL APPLICABILITY

The heat pipe of the present invention has, even when thin, excellentheat transport characteristics with a favorable maximum heat transportamount and low thermal resistance; thus, the heat pipe of the presentinvention has a high utilization value in fields such as the cooling ofthin electronic components or the cooling of electronic componentsmounted at a high density, for example.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsthat come within the scope of the appended claims and their equivalents.In particular, it is explicitly contemplated that any part or whole ofany two or more of the embodiments and their modifications describedabove can be combined and regarded within the scope of the presentinvention.

What is claimed is:
 1. A heat pipe having a heat receiving portion thatis configured to be thermally connected to a heat generating member soas to absorb heat from the heat generating member, the heat pipecomprising: a flat container having a tube shape of which both ends aresealed, the flat container having a pair of flat inner surfaces thatoppose each other in a vertical direction in cross sectionsperpendicular to a lengthwise direction of the flat container; a wickstructure housed inside the flat container; and a working fluid sealedinside the flat container, wherein in at least one cross section of theflat container: the wick structure comprises a first wick member and asecond wick member disposed in the vertical direction, the first wickmember contacts the second wick member and one inner surface of the pairof flat inner surfaces of the flat container, and both side faces of thefirst wick member do not contact any of the inner surfaces of the flatcontainer, and the second wick member contacts the other inner surfaceof the pair of flat inner surfaces of the flat container, and both sidefaces of the second wick member do not contact any of the inner surfacesof the flat container, wherein the wick structure has a first wick partand a second wick part, respectively disposed in the lengthwisedirection of the flat container, the second wick part being directly orindirectly connected to the first wick part and having a maximum widththat is wider than a maximum width of the first wick part, and whereinthe second wick part is disposed in the heat receiving portion of theheat pipe.
 2. The heat pipe according to claim 1, wherein the maximumwidth of the first wick part is 40% to 60% of a maximum width of aninner space of the flat container, and the maximum width of the secondwick part is 60% to 80% of the maximum width of the inner space of theflat container.
 3. The heat pipe according to claim 1, wherein a lengthof the second wick part in the lengthwise direction of the flatcontainer is 2% to 50% of a sum of a length of the first wick part inthe lengthwise direction of the flat container and a length of thesecond wick part in the lengthwise direction of the flat container. 4.The heat pipe according to claim 1, wherein in said at least one crosssection: a cross section of the first wick member has a convex-shapedbottom and a flat top, and a cross section of the second wick member hasa flat bottom and a convex-shaped top, and the convex-shaped bottom ofthe first wick member contacts the convex-shaped top of the second wickmember, and the flat top of the first wick member contacts said oneinner surface, and the flat bottom of the second wick member contactssaid other inner surface.
 5. The heat pipe according to claim 4, whereinthe second wick part of the wick structure is in said at least one crosssection, and in said at least one cross section, a maximum width of theflat bottom or the convex top of the second wick member is 60% to 80% ofa maximum width of an inner space of the flat container.
 6. The heatpipe according to claim 1, wherein the first wick part is disposed onone end in the lengthwise direction of the flat container, and thesecond wick part is disposed on the other end in the lengthwisedirection of the flat container.
 7. The heat pipe according to claim 1,wherein there are two first wick parts, and one of the first wick partsis disposed on one end in the lengthwise direction of the flatcontainer, and the other of the first wick parts is disposed on theother end in the lengthwise direction of the flat container, the secondwick part being disposed in a center in the lengthwise direction of theflat container.
 8. The heat pipe according to claim 1, furthercomprising a third wick part disposed between the first wick part andthe second wick part in the lengthwise direction of the flat container,the third wick part having a maximum width that is wider than themaximum width of the first wick part and narrower than the maximum widthof the second wick part.
 9. The heat pipe according to claim 1, whereinin said at least one cross section, the side faces of the first wickmember that do not contact any of the inner surfaces of the flatcontainer have a convex shape, and the side faces of the second wickmember that do not contact any of the inner surfaces of the flatcontainer have a convex shape.
 10. The heat pipe according to claim 1,wherein the first wick part and the second wick part are sintered metalcompacts.
 11. The heat pipe according to claim 10, wherein the sinteredmetal compact of the second wick part is formed of sintered powdershaving a finer particle size than sintered powders of the sintered metalcompact of the first wick part.
 12. The heat pipe according to claim 1,wherein the pair of flat inner surfaces opposing each other arevertically separated by a distance of 1.5 mm or less.
 13. The heat pipeaccording to claim 1, wherein in every cross section of the wickstructure, the wick structure comprises the first wick member and thesecond wick member disposed in the vertical direction.
 14. The heat pipeaccording to claim 1, wherein in every cross section of the wickstructure: the wick structure comprises the first wick member and thesecond wick member disposed in the vertical direction; the first wickmember contacts the second wick member and said one inner surface of thepair of flat inner surfaces of the flat container, and the side faces ofthe first wick member do not contact any of the inner surfaces of theflat container; and the second wick member contacts said other innersurface of the pair of flat inner surfaces of the flat container, andthe side faces of the second wick member do not contact any of the innersurfaces of the flat container.
 15. The heat pipe according to claim 1,further comprising a thermally conductive member attached to the heatreceiving portion of the heat pipe so as to be thermally connected tothe heat generating member.
 16. The heat pipe according to claim 1,wherein in a cross section of the heat receiving portion of the heatpipe that is different from said at least one cross section: the wickstructure comprises the first wick member and the second wick memberdisposed in the vertical direction; the first wick member contacts saidone inner surface of the pair of flat inner surfaces of the flatcontainer, and the side faces of the first wick member do not contactany of the inner surfaces of the flat container; the second wick membercontacts said other inner surface of the pair of flat inner surfaces ofthe flat container, and the side faces of the second wick member do notcontact any of the inner surfaces of the flat container; and the firstwick member does not contact the second wick member.